PHOENIX, Arizona, June 12. ABOUT 11 hours into her attempt to become the first person to swim from Cuba to Florida without the use of a shark tank, Chloe McCardel has ended her swim after a dangerous jellyfish sting made it impossible for her to continue.

The irony of jellyfish ending the 28-year-old Aussie's swim will not likely be lost on McCardel and her crew. She chose mid-June as the best time to make the swim, as the likelihood of large schools of jellyfish was lower this time of year.

A post on McCardel's Facebook page said the crew was taking her to a hospital in Key West, Fla., to treat her injuries at 10 pm Eastern Daylight Time, but did not give details on the extent of the damage the jellyfish sting did to McCardel.

Facebook post:OK, so the word is that Chloe has suffered a 'debilitating' severe jelly fish sting that made it impossible to continue. She and the team are now heading towards Key West. Once landed, we'll post further details. Thanks everyone for all your support and best wishes.

Jellyfish have been the top enemy for those attempting to traverse the Atlantic Ocean from Cuba to the United States. Even Susie Maroney, who completed the crossing in 1997 using a shark cage, had numerous stings on her body. Though the weather was cited as the official causes for their failed crossings, Diana Nyad and Penny Palfrey were both hampered by jellyfish that made swimming for an extended time quite difficult, causing them at times to not achieve the stroke rate needed to stay on course.

McCardel was making the trek across the Atlantic Ocean stretch without the aid of a wetsuit or shark tank. McCardel used English Channel rules for the swim, which do not allow wetsuits when crossing that body of water. Many official open water swimming records discount the use of wetsuits, and though the water is bound to be comfortable enough to not need a full-body suit, wetsuits would have protected against jellyfish stings.

The swim was expected to take about 60 hours. That's twice as long as it took McCardel to do a double crossing of the English Channel, something she did twice in 2010 and 2012.

In addition to breaking the record, McCardel was swimming to raise money and awareness for cancer research, spurred on by her mother's breast cancer diagnosis 14 years ago.